Multiplex broadcasting system



Mf /s Au 5 1930. E, R. TAYLOR ET AL 1,772,168

NULTIPLEX BROADCASTING SYSTEM Filed April 28. 1927 2 Sheets-Sheet 1 vmmvrons EB]ZZ 101w? BY QB mom 7 A TTORNEY Aug. 5, 1930. E. R. TAYLORMULTIPLEX BROADCASTING SYSTEM Filed April 2a. 192'r 2 Sheets-Sheet 2INVENTORS 5"" JYams-om E121 BY 0.

ATTORNEY Patented Aug. 5, 1930 UNITED STATES PATENT OFFICE EDMUND R.TAYLOR, OF NEW YORK, N. Y., AND OSCAR B. HANSON, OF ROSELLE, NEW

JERSEY, ASSIGNORS TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A COR-IPORATION OF NEW YORK MULTIPLEX BROADCASTING SYSTEM Application filedApril 28,

This invention relates to multiplex broadcasting systems, andparticularly to arrangements in such systems for interconnecting aplurality of sources of news, music or the like with a plurality oftransmitting stations, so that the programs originating at said sourcesmay be simultaneously broadcast by said transmitting stations.

There will be shown herein a system for operating a plurality ofbroadcasting studios in connection with a number of transmittingstations. A particular form of interconnecting system is describedherein, merely for the sake of illustration, and is so arranged that anyone of the studios may be connected to any one of the transmittingstations, two studios not being connected to any one transmittingstation at the same time. This is accomplished in a manner such that theaudiences of the various transmitting stations do not hear any of theswitching noises and do not observe any, apprec,,iable delays betweenselections, or that any other program is being transmitted by any othertransmitting 25 station except the one the audiences are scheduled torecelve.

It is one of the objects of this invention to provide in a multiplexbroadcasting system interconnecting a plurality of transmitting stationsthrough a control room, a telephone intercommunication circuit, so thatthe announcers in the various studios may be connected telephonically tothe operator or operators in the control room. Accordingly, there willbe shown herein a system whereby any announcer may speak to the controlroom operator associated with his studio, and vice versa.

It is another object of this invention to provide in a multiplexbroadcasting system interconnecting a plurality of studios and aplurality of transmitting stations through a control room, a telephoneinterconnecting circuit, so that an operator at any one of thetransmitting stations may be connected telephonically with the operatoror operators at the control room and with the announcer or announcers atthe various studios.

It is another object of this invention to provide a monitoring circuitor circuits in a radio 1927. Serial No. 187,273.

broadcasting system, so that anyone in a studio where program matteroriginates may monitor the program matter as it is being transmittedthrough the control room, or as it is being transmitted by thetransmitting station. In the particular circuit to be describedhereinafter, a person in any one of the studios may monitor the programmatter transmitted from any one of the studios.

It is another object of this invention to provide in a multiplexbroadcasting system interconnecting a plurality of studios with aplurality of transmitting stations through a control room, means toindicate to the announcers in the various studios that the apparatus andequipment at the control room are ready for the transmission of programmatter through some or all of the various transmitting stations.

And it is a further object of this invention to provide signals at thevarious transmitting stations to indicate to the operators at saidtransmitting stations that program matter should be coming into theirstations from the various studios.

While the nature of the invention will be pointed out with particularityin the appended claims, the invention itself, both as to its furtherobjects and features, will be better understood from the detaileddescription hereinafter following when read in connection with theaccompanying drawing, in which Figs. 1 and 2, when placed side by side,show one application of the rinciples of this invention to a multiplexroadcasting system.

Referring to the drawing, there is shown a multiplex broadcasting systeminterconnecting two studios A and B, and three transmitting stationscomprising radio transmitters ST 8T and ST and corresponding radioantennae TA TA and TA,. These studios and transmitting stations are sointerrelated that the programs originating at these studios may besimultaneously broadcast by the transmitting stations, the system beingso interlocked that both studios may not be connected to any onetransmitting station at the same time. Each studio has three controlrelays, one control relay corresponding to each transmitting station. Atstudio A, these control relays are designated by the referencecharacters R R and R and at studio B, these relays are designated by thereference characters R R and R Some of the apparatus for connecting oneof the studios with a particular transmitting station is located at thatstudio, and the rest of the apparatus is located at the control room.Each studio has a program microphone or microphones and an announcersmicrophone or microphones. Moreover, a nemo circuit is connected to eachstudio so that the program from some distant pickup point may be broughtinto the studio in order to be transmitted through an appropriatetransmitting station. Yet, it will be understood that while only onenemo circuit is shown connected to any one studio, any number of thesenemo circuits may be connected to the studio, within the scope of thisinvention, apparatus being provided to switch the apparatus at thestudio from one nemo circuit to another nemo circuit associatedtherewith. The program microphones MP and MP the announcers microphonesMA and MA and the nemo circuits NC and NC correspond, respectively, tostudios A and B. Switches K and K and K and K are also located at therespective studios, so that any one or more of the transmitting stationsmay be transferred by these switches to one or the other of the studiomicrophones or to the microphones at some distant pick-up pointsconnected to the corresponding nemo circuits. Studios A and B terminatein studio bus-bars Sb and S6 respectively. The transmittin stations areconnected through line ampli ers LA LA and LA to corresponding channelbusbars CB CB and CB respectively.

For the sake of convenience, the course of transmission from one of thestudios, studio A, to one of the transmitting stations, such as thestation associated with the channel bus-bar CB will now be considered insomewhat greater detail. At studio A, there is a microphone controlpanel CP which adjoins the program microphone MP and the announcersmicrophone MA Suitable means (not shown) is associated with themicrophone control panel GP for feeding current from a battery (notshown) to either or both of these microphones, and still other means(not shown) is provided for observing the magnitude of the currentflowing from the battery through the particular microhone connected tothe control panel (3P t will be understood that these microphones may beof any well-known, type, as, for example, of the type known as thecarbon transmitting microphone, or of the type known as the condensermicrophone, with the amplifier usually associated therewith.

It is to be remembered that the equipment at studio B is shown hereinsimilar to the equipment at studio A, and that the descrip tion of theequipment at studio A' applies equally well to the description of theequipment at studio B.

The circuits connected to the microphone control panel CP have becomeknown as the program and announcers circuits. These circuits areconnected, respectively, to the lower contacts 9' and is of the switchesK and K A nemo circuit N0 is connected to the contacts a and b of theswitch K Switches K and K are so arranged as to connect the programmicrophone MP the announcers microphone MA or the nemo circuit NC withthe input of the amplifier CA at the control room.

Three lamps L L and L at studio A are also controlled by the switches Kand K and indicate to the announcer whether switches K and K have beenoperated to connect the program microphone MP the announcers microphoneMA or the nemo circuit NC with the amplifier CA These connections willbe described in somewhat greater detail hereinafter.

The main transmission path may be followed from the contacts 6 and f ofthe switch K through the amplifier CA at the control room, which isterminated in a suitable impedance PT through the inner contacts b and cof the main relay R to the studio bus-bar S5,. The main relay Rfunctions to open the circuit between studio A and the correspondingbus-bar $6 at times when it is considered undesirable to transmit theprogram matter originating in studio A. A volume indicator LL is bridgedacross the main transmission path between the amplifier CA and theterminating impedance PT both at the control room, to indicate thetransmission volume or level after amplification. The magnitude of theterminating impedance PT mentioned hereinabove, is low as compared tothe magnitude of the impedance in the inputs of the line amplifiers LALA and LAg, so that when one of the amplifiers, such as LA is connectedto the studio bus-bar Sb the other amplifiers LA and LA either or bothof them, may be also connected thereto or disconnected therefrom withoutappreciably affecting the amount of energy transmitted by the amplifierLA This is so because most of the energy transmitted by the amplifier CAis expended in the terminating impedance PT which is of a smallmagnitude, and because very little of the energy is expended in theinput of each line amplifier.

n order to minimize the possibility of crosstalk between studio bus-barsor channel busbars when the studio bus-bar Sb is disconnected from theamplifier CA a contact is closed by armature d of the main relay Rthereby short-circuiting the studio busbar SL so that when the mainrelay R is not energized, the line relays LE LE and LR similarly becomeshort-circuit-ed, so that program matter can not be transmitted to theseline relays. Accordingly, any voltages which may be induced in thesecircuits are prevented from being impressed upon the input of the lineamplifiers LA LA and LA and are further prevented from being amplified,all of which would cause objectionable cross-talk or interference. Theoperation of the line relays LE LR and LR will be described in somewhatgreater detail hereinafter.

13 The system is so laid out that either of the studios may be connectedwith one or more transmitting stations simultaneously, and, moreover, sothat any transmitting station may be connected to any studio. Theinterlocking arrangement shown herein prevents any one transmittingstation from being connected to both studios at the same time. This isessential to prevent confusion between programs. The omission of aninterlocking arrangement would permit the tying together of two or morestudio bus-bars in the corresponding studios to the same transmittingstation. The line relays LE LE and LR and LR- LR, and LE associated withthe studios A and B, respectively, are

so arranged as to prevent any one transmitting station from beingconnected to both studios at the same time. Failure of operation, orimproper operation of these line relays LR, and LR, would permit thetransmitting station associated with the channel bus-bar CB to becomeconnected to studios A and B simultaneously. Improper operation of theother line relays will produce similar undesirable effects.

The studios and the control room are provided with signaling devices tokeep the announcers at the studios and the operator or operators at thecontrol room continuously advised of the manner in which the studios areconnected with the various transmitting stations. Means are provided topermit the announcer at either studio to connect his studio to one ormore of the transmitting stations. After his studio has been connectedto these transmitting stations, the system is arranged so that the otherstudio can not be connected to the same transmitting stations at thesame time. Thus, the announcer at any studio has at his disposalapparatus for picking up and for releasing the various transmittingstations, and he has also various signaling devices which keep himcontinuously advised as to whether or not the various transmittingstations are already connected to his studio or to the other studio. Adescription of the apparatus mentioned hereinabove will be described insomewhat greater detail hereinafter.

In studio A, keys K although shown as permanent keys, may be K,,, whichare momentary contact keys and control the operation of relay R Byclosing key K relay R becomes energized by the flow of current throughthe winding of that relay from a battery B the circuit including thearmature of the relay IR conductor 21, key K the winding of relay R keyK key K conductor 22, key K and ground. As the winding of the relay Rbecomes energized, its armature A closes a contact 0, enabling theWinding of the relay R to receive current from a battery B at the sametime that current is flowing through the winding of that relay fromabattery B The circuit from battery B includes key K conductor 23, key Kthe armature A and the contact 0 of the relay R the winding of the relayR key K key K conductor 22, key K and ground. After contact 0 of therelay R has been closed by armature A of that relay, relay R remainsenergized even after key K is released. Shortly after contact 0 of therelay R is closed by armature A, another contact (1 is closed byarmature A. Current then flows from the battery B through the windin gof the relay IR this circuit including the battery E the key K conductor23, the key K armature A of the relay R contacts 0 and (Z of the relay Rconductor 24, the wind ing of the relay IE and ground. Thus, as thearmature A of the relay R closes its contact (Z, the relay 1R becomesenergized to enable its armature to open the contact associatedtherewith, thereby disconnecting battery 13 from the winding of therelay R Yet, the winding of the relay It, remains energized by the flowof current from the battery B through the circuit including the key Kconductor 23, key K armature A and contact a of the relay R the windingof the relay R key K key K conductor 22, key K and ground. However,current may flow through the key K at studio B only when the relay 1R isdeenergized. After relay R, has operated to close contact d, and afterrelay IR has become energized, the relay R at studio B can not becomeoperated by key K, at that studio until the relay 1R has first becomedeenergized.

The winding of the line relay LR is in parallel relationship with thewinding of the relay R conductor 25 connecting these windings.Consequently, the energization or deenergization of the relay R causes acorresponding action of the line relay LR The armatures a and b of theline relay LR are connected through the channel bus-bar CB to the lineamplifier LA the radio transmitter ST} and the transmitting antenna TATherefore, when the line relay LR and the relay R become energized, themain transmission circuit between the studio A and the transmittingstation associated with the bus-bar CB becomes closed. Also, the

lamp L at the studio indicates to the announcer that the relay R, hasoperated. Similarly, the lamp L at the control room indicates to theoperator thereat that the line relay LR has operated. The circuit of thelalnp L includes a battery B the lamp L the armature c of the line relayLR and ground. The relay R at studio A may be deenergized by operatingkey K key K or key K these keys all being included in a series pathwhich includes the winding of the relay R Keys K and K are also inseries with the windings of relays R and R at studio A, and hence arethe studio and control room master release keys, respectively.

hen the apparatus in the control room is ready for the transmission ofprogram matter to a given radio transmitting station, such as the oneassociated with the radio transmitter 8T the operator at the controlroom operates a key SK in order to signal the announcers in the studiosthat the apparatus is ready for the transmission of program matter. Afeature of this invention lies in the provision of a link tying thissignal with apparatus at the radio transmitting station in such a.manner that the signal can not be given unless the carrier wave,characteristic of that transmitting station is on the air. \Vhen thecarrier frequency characteristic of the radio transmitter ST is beingradiated by the radio antenna TA some of the energy radiated by theantenna TA is picked up by a coil Coupled to the antenna. The coil V isconnected to a detector, shown herein as a vacuum tube detector, thecoil bridging a condenser C and being connected between the grid andfilament of the vacuum tube V A battery B is connected to the filamentof the vacuum tube V through a resistance Z this filament being heatedto an electron-emitting temperature by the current flowing from batteryB The output circuit of the vacuum tube V includes a battery B thefilament and plate of the vacuum tube V and the winding of a relay R\Vhen radio frequency energy, characteristic of the radio transmitterST,, is picked up by the winding V the winding of the relay R willbecome energized due to the flow of current therethrough from battery 13which is above a definite minimum value. Consequently, the armature ofrelay R will become attracted to close the circuit of another relay R atthe control room, current flowing from a battery 13 through the windingof the relay R the armature and contact of the relay R and ground. Whenthe winding of the relay R becomes energized, its armature is attractedto close a contact associated therewith, thereby grounding the armature.Similarly, relays R and E are associated with vacuum tubes V and V inthe input circuits of which are coupling coil W, and

condenser C and coupling coil 'W and condenser C the windings W and Wrendering relays R and R operative when currents characteristic of radiotransmitters ST and 8T are being radiated by the transmitting antennaeTA and TA respectively. Similarly, there are relays R and R at thecontrol room, which become energized by the flow of current therethroughfrom batteries B and B when the armatures of the relays R and R areattracted, respectively,thereby grounding the armatures connected tothese relays.

In order that the announcer at studio A may know which transmittingstations are prepared to receive and broadcast the program originatingat his station, lamps L L and L are provided at that studio, each lampbeing associated with one of the transmitting stations, these lampscorresponding to relays R R and R respectively. Lamps L L and L atstudio A, and lamps L L and L, at studio B are controlled by the signalkeys SK SK and SK respectively, which are located at the control room,and which are under the supervision and control of the operator at thecontrol room. The system is so arranged that when one of the relays,such as R becomes operated, the lamp L, at studio B corresponding to therelay R at that. studio will become extinguished. Thus. the lamp Ladvises the announcer in studio A that the carrier wave of thetransmitting station associated with the channel bus-bar CB is on theair and that the transmission path to that transmitting station is readyfor broadcasting service from studio A. By operating one of the signalkeys, such as SK a lamp L becomes illuminated, current flowing from thebattery B, through the lamp Li the key SK the armature of the relay Rand ground. The lamp L at the studio also becomes illuminated,regardless of the state of energization of the relay R as will be shownmore clearly hereinafter. Vhen the winding of the relay R isdeenergized, current flows from the battery B through the armature ofthe relay 1B,, the conductor 21, contact 7 and armature B of the relay Rlamp L key SK the armature of the relay R, and ground. lVhen the windingof the relay R becomes energized, current then flows from the batteryB,- through the key K conduct-or 2?), key K contact e and armature B ofthe relay R lamp L key SK the armature of the relay R and ground.Similarly, the lamp L in studio 13 becomes illuminated by closure of thekey SK regardless of the state of energization of relay R currentflowing through lamp L, from battery B when the relay R is deenergized,and current flowing from the battery B through the lamp L when the relayR becomes energized. Yet, when the winding of the relay R in studio Abecomes energized, the corresponding lamp L in studio B becomesextinguished, while the lamp L in studio A remains illuminated. Thus,there is an indication to the announcer in studio B that thetransmitting station connected to the channel bus-bar C13 is notavailable for the transmission of program matter originating at hisstudio. Obviously, when relay R at studio A again becomes deenergized,both lamps L and L, at studios A and B, respectively, again becomeilluminated, thus again providing an indication for the operators atboth studios that the transmitting station connected to the channelbus-bar CB is again available for the transmission of program matter.

Keys K and K and K and K are the master release keys, keys K and K beingunder the supervision and control of the announcers at studios A and B,respectively, and keys K and K being under the supervision and controlof the operator or operators at the control room. The keys at studios Aand B permit the announcers at these studios to release any one or moreof the program transmitting stations from their re spective studios. Thekeys K and K at the control room break the circuits of batteries B and Band ground, respectively, thereby releasing relays R R and R at studioA, and relays R R and R at studio B, respectively. The keys K and K atstudios A and B similarly release relays R R and R at studio A, andrelays R R and R at studio B, respectively. Thus, the system enableseither the announcer in the studio or the operator in the control roomto simultaneously release all of the transmitting stations connected tohis (the announcers) studio.

In studio A, the output of the announcers microphone MA passes throughthe micro phone control equipment. OP to the lower contacts j and 7c ofthe switch K The output of the program microphone MP simi larly passesthrough the microphone control equipment CP to the lower contacts 3' and7c of the switch K The nemo circuit NC is connected to the uppercontacts a and Z) of the switch K The upper contacts a and b of theswitch K are connected to the blades 6 and f of the switch K The bladese and f of the switch K are connected to the input of the' amplifier CAat the control room. lVhen the switch K is thrown downwardly to engagecontacts 9' and k, the announcers microphone MA is then connected to theamplifier CA By throwing the switch K upwardly to engage contacts a andZ2, and by throwing switch K downwardly to engage contacts and is, theprogram microphone MP will then be connected to the amplifier CA Bythrowing both switches K and K to their upward positions, the nemocircuit NC will then be connected to the amplifier CA By leaving switchK in its upward position, and by operating switch K the announcer atstudio A may connect either the announcers microphone MA or the nemocircuit N C to the amplifier CA A lamp L is located at studio A andprovides an indication to the announcer at studio A that the equipmentof the control room corresponding to studio A is in readiness foroperation. Clearly, the lamp L may, if desired, be a colored lamp todistinguish this lamp from some or all of the other lamps. By closing akey K at the control room, the control rooln operator then sends currentfrom a battery B, through the lamp L at studio A, this circuit includingthe battery 13 key K conductor 27, lamp L and ground. Another lamp Lwhich is located at the control room, is also operated by key K Thecircuit of lamp L includes the battery B the key K the lamp L andground. It is to be noted thatthe winding of the main relay R at thecontrol room can not become energized unless the key K in the controlroom has first been closed. This will prevent the transmission ofprogram matter to one or more of the radio transmitting stations beforethe proper connections have been made at the control room.

The main relays R and R at the control room open the main transmissionpaths between studios A and B and the studio busbars SI), and S5respectively, whenever it is considered undesirable to transmit thesounds originating in the studios. Again confining the description ofthe apparatus at the control room to that which corresponds to studio A,it is apparent that one terminal of the winding of the main relay R isgrounded, and that the other terminal of the winding of the main relay Ris connected through conductor to the contacts 0 and l of the switch KThe blade 9 of the switch K is connected to the battery B at the controlroom through conductor 27 and key K when key K is closed. Thus, when keyK is closed, the operation of the switch K at the studio to close eithercontact 0 or contact Z will permit current to flow from the battery B,at the control room through conductors 27 and 40, and through thewinding of the relay R When the winding of the relay R becomesenergized, one of its armatures a closes a contact which permits currentto flow from the battery B to the lamp L this circuit being closedthrough the armature a of the relay R and ground. Lamp L indicates tothe operator at the control room whether or not relay R has operated.The contacts 6 and c of the relay R control the transmission through themain transmission path between the amplifier CA at the control roomandthe studio busbar S6 When the winding of the relay R is not energized,the armature d of this relay shortcircuits the studio bus-bar S6 therebyshort-circuiting all of the line amplifiers connected thereto.

When the key K at the control room is operated, causing lamp L at thestudio to become illuminated to provide an indication to the announcerat studio A that everything in the control room is in readiness fortransmission of program matter originating in that studio, and when theswitches K and K at the studio are operated to connect either theprogram microphone MP or the announcers microphone MA or the nemocircuit NC to the amplifier CA at the control room, either lamp L L or Lwill be illuminated at the studio to indicate to the announcer which ofthese sources has been connected to the amplifier CA at the controlroom. The circuit for lamp L includes the battery B the key K conductor27, blade h and contact (1 of the switch K blade g and contact Z of theswitch K lamp L and ground. The circuit for lamp L includes the batteryB key K conductor 27, blade h and contact m of the switch K lamp L andground. The circuit for lamp L includse the battery B key K conductor27, blade in and contact d of the swtich K blade 9 and contact 0 of theswitch K lamp L and ground. A lamp L is controlled by a relay R both ofwhich are at the control room, the lamp providing a visible indicationto the operator at the control room that the announcer at studio A hasset up his equipment so as to transmit program matter coming over thenemo circuit NC The winding of the relay R is connected to a battery Bat studio A through a conductor 41, the contact d and the blade h of theswitch K Inasmuch as the switch K must be thrown to its upward positionto connect the nemo cir cuit NC to studio A, the relay R at the controlroom will thereupon become energized, attracting its armature andilluminating lamp L by the flow of current therethrough from a battery BSimilarly, a relay R controls a single lamp L to provide a visibleindication to the operator at the control room that the announcer atstudio B has set up his equipment so as to transmit the program mattercoming over the nemo circuit N0 I he line relays LE LR and LEcorresponding to studio A, and the line relays LBJ, LE and LEcorresponding to studio B, are so arranged that the line amplifiers LALA and LA may be switched from one studio bus-bar, such as S6,, to theother studio bus-bar S71 This has already been explained hereinabove.Yet, in each of the line relays, such as LB one terminal of the windingof the relay 1s connected to an armature c of that relay, both beinggrounded. The operation of the line relay LR illuminates a lamp L by theflow of current therethrough from a battery B thereby providing anindication that the line relay LE has operated. The armatures a and b ofthe line relay LE control the main transmission path between the studiobus-bar SB and the line amplifier LA The other terminal of the windingof the line relay LR is connected to the winding of the relay R instudio A. These windings are in parallel relationship and consequentlyare simultaneously energized or deenergized.

One of the features of this invention is the provision of a telephonecommunication system between the announcers in the various studios andthe operator or operators in the control room, so that telephone servicemay be very promptly obtained. In this invention, a telephone systeminterconnects each studio with the control room, permitting theannouncer in the studio to speak to the control room operator associatedwith his studio. Keys TK and TK T K and TK are located in studios A andB, respectively. TVhen the announcer in studio A closes the telephonekey TK and lamp L at the control room lights up, current flowing from abattery B through the key T K conductor 50, lamp L and ground. Thus, theannouncer at studio A attracts the attention of the operator at thecontrol room, advising him that he desires to communicate with himtelephonically. It

will be understood, however, that lamp L or other visual means, wouldnot be necessary at the control room to attract the control roomoperators attention if the operator atthe control room continually worea telephone headset. Similarly the operator at studio B may attract theattention of the operator at the control room by operating a telephonekey TK, at his studio, lamp L then becoming illuminated. Keys K and Kare located atthe control room, one associated with each studio, thesekeys being employed to advise the announcers in the studios that theoperator or operators in the control room desire to speak to theannouncers in the studios by telephone. By closing key K at the controlroom, a lamp L at studio A is illuminated, current flowing from abattery B at the control room through the key K conductor 51, lamp L andground. Similarly, lamp L at studio B indicates to the announcer at thatstudio that the control room operator desires to have a telephoneconversation with him. Yet, it will also be understood that these visualmeans would not ordinarily be necessary if the announcers at the studioswere equipped with telephone headsets.

The telephone key 'TK and the lamp L and the telephone key TK and thelamp L are located, respectively, in studios A and B, key TK beingoperated by the announcer in studio A to illuminate lamp L in studio Bwhenever the announcer in studio A desires to connect his telephonecircuit to the telephone circuit in studio B, telephone key TK in studioB being operated to illuminate lamp L at studio A whenever the announcerin studio B desires to connect his telephone circuit to the telephonecircuit at studio A. hen the announcer in studio A closes the telephonekey TK current flows from battery B at studio A through the telephonekey TK conductor 52, lamp L at studio B, and ground. A telephonesubstation circuit 813,, including a telephone transmitter and atelephone receiver of any well known type, is connected to asimilar-telephone substation circuit SB at studio B, telephonic currentsflowing from the substation circuit SB at studio A, through key TK,,conductors and 54, telephone key TK, at studio B, and the telephonesubstation circuit SE Similarly, when the announcer at studio B operatesthe telephone 1 key TK, at his studio, current flows from a battery B atstudio B, through the key TK conductor 55, lamp L30, at studio A, andground. Telephonic currents flow between the telephone substationcircuit S13 at studio B, and the telephone substation circuits SB atstudio A as soon as the announcer at studio A operates telephone key TKIt is another feature of this invention to provide a telephone circuitbetween the announcer in one of the studios, the operator at the controlroom and the operator at one of the radio transmitting stations, theradio station operator being therefore connect-ed telephonically withthe control room operator and with the announcer in the studiofurnishing the program. Accordingly, relays TR TR and TR and relays TR,,TR] and TR, are located in the control room, relays TR and TR,corresponding to the radio transmitting station connected to the channelbus-bar CB relays TP and TR! corresponding to the radio transmittingstation connected to the channel bus-bar CB and relays TR and T Rcorresponding to the radio transmitting station connected to the channelbus-bar CB3. These relays are normally controlled by the line relays atthe studio. In connection with studio A and the apparatus at the controlroom associated therewith, it may be said that the line relay LRcontrols the operation of the relay TR through the armature of the linerelay LE Thus, when the line relay LR becomes operated. armature c isattracted, energizing the winding of the relay TR current flowing fromabattery B through the winding of the relay TR telephone key TIL,armature c of the line relay LR and ground. Similarly, the operation ofthe armature c of the line relays LE and LR. control the operation ofthe telephone relays TR and TR current flowing from batteries B and Bthrough the windings of these relays and through the telephone keys TKand TK respectively.

Accordingly, when one of the line relays, such as LE is operated toconnect studio A to the radio transmitting station connected to thechannel bus-bar CB the corresponding telephone relay TR at the controlroom is operated to connect the telephone substation circuit T13 locatedat the same radio transmitting station. to the telephone substationcircuit SB at the control room, and, if the telephone key TK at studio Ais closed, to the telephone substation circuit SB at studio A.Similarly. the operation of the line relays LR, and LR bring about theoperations of the corresponding telephone relays TR and TH respectively,to connect the telephone substation circuits TB and T13 at the radiotransmitting stations connected to the channel bus-bars CB and CBrespectively, to the same telephone substation circuit SB at the controlroom, and, if the telephone key TK at studio A is closed, to thetelephone substation circuit SB at that studio. Telephone substationcircuits TB TB and TB located at the transmitting stations connected tothe channel bus-bars CB CB and CB respectively. may be connected to atelephone substation circuit S13 at the control room through theoperations of the telephone relays TR, TR, and TR respectively, and, ifthe telephone key TK at studio B is closed, to the telephone substationcircuit SE at that studio.

The telephone relays have been shown hereinabove to be controlled by theline relays. These telephone relays may be controlled by the telephonekeys at the control room. The telephonekeys TK TK and TK may be used tocontrol telephone relays TR TR and TR and the telephone keys TK TIL. andTK may be used to control the telephone relays TR, T11 and TRrespectively. In connect-ion with studio A, it may be said that theoperator at the control room may connect his substation circuit S13 tothe substation circuit TB at the radio transmitting stationcorresponding to the channel bus-bar CB by closing key TK Vhen key TK isclosed, a telephone relay TR is energized by the flow of current frombattery B through the winding of that relay, through key TK and ground.The arma-' tures of the relay TR are attracted, thereby connecting thetelephone substation circuit SB at the control room, to the telephonesubstation circuit TB at the radio transmitting station. Similarly, theoperation of the keys TK and TK may be used to connect the telephonesubstation circuit SB at the control room, to the telephone substationcircuits TB and TB, at the radio transmitting stations associated withthe channel bus-bars CB and CB respectively. It will be obvious thatwhile only one telephone substation circuit has been shown herein at thecontrol room, operatively associated with the telephone keys TK ,.TK andTK separate telephone substation circuits may be connected to thevarious telephone substation circuits at the radio transmitting stationsT13 T13 and TB;,, respectively.

Relays SR SR and SR, are provided at the control room, and are energizedwhen the corresponding line amplifiers LA LA and LA are ready for use.but are not connected to a studio bus-bar. The inputs of these lineamplifiers will become short-circuited by the armatures of the relays SRSR and SR when the line relays are operated. In other words, when theline relays LE LR and LE corresponding to studio A, and the line relaysLR], L11 and LE corresponding to studio B are not energized, relays SRSB and SR at the control room. will be operated. The relays SR SR andSR, are interlocked with the relays IR IR and IR the signal keys 5K SKand 8K and the relays R R and R respectively. The interlocking of thesekeys and relays permits the operation of relays SR SB: and SR only whenthe signals keys SK SK and SK, are closed, when the relays 1B IE and IRare unoperated, and when the relays R R and R are operated,respectively. For the sake of simplicity, the operation of only one ofthese relays, SR will be considered. One terminal of the winding of therelay SR, is connected to ground through conductor 29, the middlecontact of the key SK and the armature of the relay R The other terminalof the winding of the relay SR is connected to battery B at the controlroom, through conductor 30, conductor 21 and the armature of the relay1R Therefore, upon closure of the signal key SK current will flow frombattery B through the winding of the relay SR thereby operating saidrelay. The armature of the relay SR is then attracted, providing ashort-circuit for the input of the line amplifier LA Relay SR is alwaysoperated to put a short circuit on the input of the amplifier LA whenthe signal key SK is closed, when the relay IE is unoperated and whenthe relay R is operated. \Vhen the winding of the relay 1R becomesenergized, as, for example, when the relay R in studio A, becomesenergized, the circuit connecting battery B at the control room, and thewinding of the relay SR is opened, deenergizing the winding of relay SRremoving the short-circuit from the input of the amplifier LA andplacing this channel in an operative condition. Similarly. relays SR andSR are energized by current from battery B at the control room throughthe armatures of relays IE and IE conductors 31 and 32. the middlecontacts of signal keys SK and SK the armatures of relays R and Brespectively, and ground.

One of the features of this invention is the provision of a monitoringsystem for monitorin the output of each studio while the program matteris being passed through the studio and through the amplifier at thecontrol room. This permits the announcer in the studio, or the artistspeaking into the microphone to determine whether the program matter isbeing transmitted from the studio to the control room. Accordingly theoutputs of the amplifiers CA and CA are multiplied to studios A and Bthrough resistances R and R and conductors and 61, and throughresistances R and R and conductors 62 and 63, respectively. Conductors60 and 61 terminate in a jack J at studio A, so that the operator at thestudio, or the artist speaking into the microphone may monitor his owncircuit if he connects a plug P to jack J plug P being connected to aheadset H Conductors 62 and 63 are connected to a jack J so that theannouncer. or artist at studio B may, upon connecting plug P into ack Jmonitor the output of studio B after the program matter is transmittedthrough the amplifier CA at the control room, plug P at studio B beingconnected to a headset H The operator in studio A may also connect plug1? at his studio with jack J jack J being connected through conductors64 and 65, conductors 63 and 62, and through resistances R and R to theoutput of the amplifier CA at the control room, this amplifieramplifying program matter transmitted from studio B. Similarly, theoperator at studio B may connect plug 1? to jack J which is connected tothe output of the amplifier CA at the control room, through conductors66 and 67, conductors 60 and 61 and resistances R and R to the amplifierCA at the control room, amplifying the program matter transmitted fromstudio A. In accordance with this invention, the operator at any one ofthe studios may monitor the program matter transmitted from his, or fromany other studio, to the control room, which may obviously be at somedistant point. After the program matter has passed through the amplifierat the control room corresponding to the studio to be monitored. theresistances R and R and R and R these resistances being of large anddefinite magnitudes. are inserted between outputs of amplifiers CA andCA at the control room, and the corresponding jacks at studios A and B,respectively, in order that any noise or other disturbance on themonitoring circuits will have but a negligible effect on the programmatter being transmitted from the studios.

It has been pointed out hereinabove that visual signals are provided inthe control room to indicate to the operator atthe control room thatastudio is connected to a transmitting station. Similarly, visualsignals may be provided to indicate at a transmitting station that somestudio is connected to that transmitting station. In other words,

signals may be provided at each transmitting station to indicate whenprogram matter should be comin to that transmitting station. This may beaccomplished by having a circuit extend between contacts on the mainrelays and line relays, so thatwhen a main relay and an associated linerelay are operated, and the desired transmitting station is on the air,this circuit will be closed to operate a relay, for example, R at thecontrol room, the operation of this relay controlling the operation ofanother relay, R at the transmitting station, the armature of whichcontrols the illumination of the lam L at the transmitting station. Inconnection with the transmission of program matter from studio A to thetransmitting station connected with the channel bus-bar CB when the mainrelay R is operated, and when the line relay LR is also operated toconnect the output of the amplifier CA to the transmitting stationconnected to the channel bus-bar CB a circuit is closed through relay Rthis circuit including armature a of the main relay R armature d of theline relay LE the winding of the relay R battery B and ground. Relay Rbecomes energized to attract its armature. Current then flows frombattery B through the winding of the relay R at the transmittingstation, this circuit including the battery B the armature of the relayR and its contact, the winding of the relay R and ground. The armatureof the relay R is attracted, closing a circult through lamp L at thetransmittlng station, current flowing from the battery B through thelamp L through the armature of the relay R at its contact and ground.Thus, a visual signal is provided at the transmltting station toindicate to the operator at the transmitting station that program mattershould be coming to that transmitting station. Similarly, when programmatter should be coming to the transmitting stations connected to thechannel bus-bars CB and CB the relays R and R at the control room areenergized by the flow of current therethrough from batteries B and Bwhich in turn operate relays R and R at the assoc ated transmittingstations,lllummatlnglamps L and L by the fiow of current therethroughfrom batteries B and B respectively.

The phrase transmitting station or radio transmitting station, asemployed herein designates a radio transmitter, public addressequipment, an individually loaded loud speaker or any other suitablesignaling device or circuit. The word studio, as employed herein,designates a place where a program of news, music or any other soundoriginates, whether it be 1n a room ad acent to the control room, or atsome point distant from the control room, requiring a connection theretoby local or long distance telephone lines, or any other suitablesignaling medium.

While only two studios and three transmitting stations have been shownand described herein, it will be understood that the system is adaptableto connect any number of studios and any number of transmittingstations, within the scope of the invention.

Vhile no auxiliary equipment, such as equalizers, repeating coils,artificial lines, etc., are absolutely essential to the operation of thesystem, as shown herein, it is to be understood that such equipment maybe added, as found desirable, in any manner well known to the art,without departing from the spirit of the invention or from the scope ofthe appended claims.

While this invention has been shown and described in one particularembodiment, merely for the purpose of illustration, it is to be clearlyunderstood that the general principles of this invention may be embodiedin other and widely varied organizations without departing from thespirit of the invention or the scope of the appended claims.

What is claimed is:

1. In a radio broadcasting system, a plurality of studios whereinprograms originate, a plurality of transmitting stations, means forinterconnecting the various studios with the various transmittingstations so that the programs originating at any two of the studios maynot be simultaneously transmitted by any one of the transmittingstations, and means at each studio for monitoring the output of anydesired studio.

2. In a radio broadcasting system, a plu rality of studios whereinprograms originate, a plurality of transmitting stations, means forinterconnecting the various studios with the various transmittingstations so that the programs originating at any two of the studios maynot be simultaneously transmitted by any one of the transmittingstations, and means at each studio for monitoring the output of anydesired transmitting station.

3. In a radio broadcasting system, a plurality of studios whereinprograms originate, a plurality of transmitting stations, a control roomincluding means for interconnecting the various studios with the varioustransmitting stations so that the programs originating at any two of thestudios may not be simultaneously transmitted by any one of thetransmitting stations, and means extending from the control room to thevarious studios to enable the announcers in the various studios tosimultaneously and selectively monitor the program transmitted from anyof the studios.

4. In a radio broadcasting system, a plurality of studios whereinprograms originate, a plurality of transmitting stations, means forinterconnecting the various studios with the various transmittingstations so that the programs originating at any two of the studios maynot be simultaneously transmitted by any one of the transmittingstations, and means to enable the announcers in the various studios tosimultaneously monitor the outputs of their respective studios.

5. In a radio broadcasting system, a plurality of studios whereinprograms originate, a plurality of transmitting stations, means forinterconnecting the various studios with the various transmittingstations so that the programs originating at any two of the studios maynot be simultaneously transmitted by any one of the transmittingstations, and a plurality of monitoring circuits one extending from eachtransmitting stations to each studio so that the announcers in thevarious studios may simultaneously monitor the programs beingtransmitted by any of the various studios.

6. In a radio broadcasting system, a plurality of studios whereinprograms originate, a plurality of transmitting stations each employinga different carrier frequency, a control room through which passcircuits extending from the various studios to the various transmittingstations, means to permit any number of transmitting stations totransmit the program of any one studio, means to prevent the connectionof any two studios to any one transmitting station, a plurality ofamplifiers at the control room one associated with each studio, and aplurality of monitoring circuits one extending from the output of eachamplifier to the corresponding studio to enable the announcer at thatstudio to monitor the program emanating from his studio.

7. In a radio broadcasting system, a plurality of studios whereinprograms originate,

a plurality of radio transmitting stations each employing a differentcarrier frequency, a control room, a plurality of circuits extendingfrom the various studios through the control room to the various radiotransmitting stations, means at the control room to connect the varioustransmitting stations to the various studios and to prevent theconnection of any two studios to any one transmitting station, aplurality of amplifiers at the control room one corresponding to eachstudio, a plurality of monitoring circuits one extending from theout-put of each amplifier at the control room to each studio, and meansto enable the announcer at each studio to monitor through saidmonitoring circuits the output of any one of said studios.

8. The combination of a plurality of studios wherein programs originate,a distant control room, a plurality of circuits extending from eachstudio to the control room for the transmission of program matter fromthe various studios, a plurality of amplifiers at the control room onecorresponding to each studio, and a plurality of monitoring circuitseach including resistance of a definite magnitude, the resistance ofeach monitoring circuit interposing a transmission loss corresponding tothe amplification of each amplifier, each monitoring circuit extendingfrom the output of one of the amplifiers at the control room to theassociated studio, thereby enabling the announcer in any studio tomonitor the program matter originating at his studio and beingtransmitted through the control room.

9. In a radio broadcasting system, a plurality of studios whereinprograms originate, a plurality of transmitting stations each employinga different radio frequency, a control room through which pass circuitsinterconnecting the various studios with the various transmittingstations so that the programs at the various studios may besimultaneously broadcast by the various transmitting stations, means toprevent the simultaneous transmission of the program matter of twostudios through any one transmitting station, a plurality of visualindicating devices one at each studio, and means whereby said indicatingdevices may indicate to the announcers at the various studios that thecontrol room operator is prepared to transmit the program matteroriginating in said studios through the various transmitting stations.

10. In a radio broadcasting system, a plurality of studios whereinprograms originate, a plurality of transmitting stations each employinga different radio frequency, a control room through which pass circuitsinterconnecting the various studios with the various transmittingstations, a plurality of visual indicating devices one at each studio,and means extending between the various studios and the control room tooperate each indicating device in order to indicate to the announcer ateach studio that the carrier frequency characteristic of a particulartransmitting station is on the air.

11. In a radio broadcasting system, a plurality of studios whereinprograms originate, a plurality of transmitting stations each employinga different radio frequency, a control room through which pass circuitsinterconnecting the various studios with the various transmittingstations, a plurality of visual indicating devices one at each studio, aplurality 0f detecting devices one at each transmittlng station, eachdetecting device detecting some of the current of the radio frequencycharacteristic of the associated transmitting station, and means at eachtransmitting station whereby the detected current may be transmitted tothe indicating device of one of the studios in order to operatethatindicating device at the studio from which program matter is beingsupplied to that transmitting station.

12. In a radio broadcasting system, a plurality of studios whereinprograms originate, a plurality of program transmitting stations, meansfor connecting any one of the studios to one or more of the programtransmitting April, 1927.

EDMUND R. TAYLOR. OSCAR B. HANSON.

Re ferencea C1 ted Swthe 1,499,081 179-2 Maxfield l, 575, 984 250-6

